7e5t

Structural highlights

Function

FSA2_FUSSF Diels-Alderase; part of the gene cluster that mediates the biosynthesis of equisetin and fusarisetin A, 2 trans-fused decalin-containing tetramic acids with antimicrobial activity (PubMed:25770422). The PKS module of fsa1 together with the enoylreductase fsa3 catalyze the formation of the polyketide unit which is then conjugated to L-serine by the condensation domain of the fsa1 NRPS module (PubMed:25770422). Activity of the Dieckmann cyclase domain (RED) results in release of the intermediate N-desmethylequisetin also called trichosetin (PubMed:25770422). Diels-Alderase fsa2 is involved in endo-selective Diels-Alder cycloaddition to form the decalin ring of equisetin (PubMed:25770422, PubMed:28401214). Subsequent N-methylation is carried out by fsa4 to give equisetin (PubMed:25770422). The enzymatic gene responsible for the conversion of equisetin to fusarisetin A has not been identified yet and is probably located outside of the fsa cluster (PubMed:28401214).^{[1] [2]}

References

1. ↑ Kato N, Nogawa T, Hirota H, Jang JH, Takahashi S, Ahn JS, Osada H. A new enzyme involved in the control of the stereochemistry in the decalin formation during equisetin biosynthesis. Biochem Biophys Res Commun. 2015 May 1;460(2):210-5. doi:, 10.1016/j.bbrc.2015.03.011. Epub 2015 Mar 11. PMID:25770422 doi:http://dx.doi.org/10.1016/j.bbrc.2015.03.011
2. ↑ Li X, Zheng Q, Yin J, Liu W, Gao S. Chemo-enzymatic synthesis of equisetin. Chem Commun (Camb). 2017 Apr 25;53(34):4695-4697. doi: 10.1039/c7cc01929g. PMID:28401214 doi:http://dx.doi.org/10.1039/c7cc01929g